From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B972ECA0FE7 for ; Tue, 26 Aug 2025 13:58:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=0aiZeMf2NhiiIB1v34ZPRLtQef3GSv6ZteY4y12PHFg=; b=ql1YbM4bpEYLRLfVDlWoHDi3Js hPSMcDKLMPutVZqdWoXa3z4/WnRCiMPzY9pm7cD7/8yygM0D09VWWpRN1iKvPkwcPPxIvf3ff5N6+ FSoSdWvddgLoPtr/QOHigJxxD3r43qyexYu19kC80jvAt4+ZbqZmZetU6SyXJMJvr41l19yK6GlWM CD6N/HWY3ALbNNQXrmyrY1+u5WoDvFQJyeRVOiiO/FWt68kL7zo9x/snnkh3cZ5nvWyshRwOemMgN g+rzzAyHiHkSlA7GX5iU0X27qLbgYIdxgURAGt7jwpIZoo3T7wxpX9LDE6y0Pc5VqYtRlHROcgW0Z AW9m7uMQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uquCL-0000000CAeP-29BL; Tue, 26 Aug 2025 13:58:53 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uqtjI-0000000C6Nd-1kGI; Tue, 26 Aug 2025 13:28:53 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 742EB1A25; Tue, 26 Aug 2025 06:28:43 -0700 (PDT) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A56233F63F; Tue, 26 Aug 2025 06:28:45 -0700 (PDT) Date: Tue, 26 Aug 2025 14:28:43 +0100 From: Mark Rutland To: Peter Zijlstra Cc: Robin Murphy , mingo@redhat.com, will@kernel.org, acme@kernel.org, namhyung@kernel.org, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, imx@lists.linux.dev, linux-csky@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-pm@vger.kernel.org, linux-rockchip@lists.infradead.org, dmaengine@vger.kernel.org, linux-fpga@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, coresight@lists.linaro.org, iommu@lists.linux.dev, linux-amlogic@lists.infradead.org, linux-cxl@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH 16/19] perf: Introduce positive capability for sampling Message-ID: References: <20250826130806.GY4067720@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250826130806.GY4067720@noisy.programming.kicks-ass.net> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250826_062852_495432_88B2D15B X-CRM114-Status: GOOD ( 19.20 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Aug 26, 2025 at 03:08:06PM +0200, Peter Zijlstra wrote: > On Wed, Aug 13, 2025 at 06:01:08PM +0100, Robin Murphy wrote: > > Sampling is inherently a feature for CPU PMUs, given that the thing > > to be sampled is a CPU context. These days, we have many more > > uncore/system PMUs than CPU PMUs, so it no longer makes much sense to > > assume sampling support by default and force the ever-growing majority > > of drivers to opt out of it (or erroneously fail to). Instead, let's > > introduce a positive opt-in capability that's more obvious and easier to > > maintain. > > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > > index 4d439c24c901..bf2cfbeabba2 100644 > > --- a/include/linux/perf_event.h > > +++ b/include/linux/perf_event.h > > @@ -294,7 +294,7 @@ struct perf_event_pmu_context; > > /** > > * pmu::capabilities flags > > */ > > -#define PERF_PMU_CAP_NO_INTERRUPT 0x0001 > > +#define PERF_PMU_CAP_SAMPLING 0x0001 > > #define PERF_PMU_CAP_NO_NMI 0x0002 > > #define PERF_PMU_CAP_AUX_NO_SG 0x0004 > > #define PERF_PMU_CAP_EXTENDED_REGS 0x0008 > > @@ -305,6 +305,7 @@ struct perf_event_pmu_context; > > #define PERF_PMU_CAP_EXTENDED_HW_TYPE 0x0100 > > #define PERF_PMU_CAP_AUX_PAUSE 0x0200 > > #define PERF_PMU_CAP_AUX_PREFER_LARGE 0x0400 > > +#define PERF_PMU_CAP_NO_INTERRUPT 0x0800 > > So NO_INTERRUPT was supposed to be the negative of your new SAMPLING > (and I agree with your reasoning). > > What I'm confused/curious about is why we retain NO_INTERRUPT? I see from your other reply that you spotted the next patch does that. For the sake of other reviewers or anyone digging through the git history it's probably worth adding a line to this commit message to say: | A subsequent patch will remove PERF_PMU_CAP_NO_INTERRUPT as this | requires some additional cleanup. Mark.